Aluminum type matrix



Patented Sept. 15', 1931 UNITED S A ES PATENT oF ICE mm wmacn wmrrz, orammonia, rnmimvnn m, nssnmon'ro Armumun comm or AMERICA, or msnmn,rmmsxpvanm, a conroaa'rron or PENNSYLVANIA Io Drawing.

i i This invention relates'to the manufacture of molds for casting typemetal and the like and it is particularly concerned with the pfovisionof satisfactory type matrices made from aluminum and aluminum alloys.

The ease with which aluminum and its alloys may be formed or machinedinto intricate and ordinarily difiicult shapes has created ademand-for-type matrices 0r molds made of this metal. It is an essentialproperty of such a mold that it retain, during the casting process, thesharp outline of the mold cavity so that the type made therein will beof standard size and feature and will not have defects which are sooften caused by the wearing action of the hot metal on the mold ormatrix. Extensive use of matrices made from aluminum and its alloys, andparticularly those alloys which are termed so strong aluminum alloys,has shown that after a few type have been cast in the mold, the moldoften fails in the sense that the mold cavity loses its sharp outlineand the type cast therein is therefore imperfect.- Although variousaluminum alloys have been experimented with in an effort to overcomethis difficulty and various standard heat treatments have been appliedto those alloys which respond to such treatments, the abovementioneddifli'culties have never been entirely overcome and therefore the use ofaluminum alloys in type matrices has been ourtailed because of the lackof a uniform product.

It is the object of this invention to provide aluminum type matrices ormolds which are uniform in character and from which a large number ofcasts may be obtained without failure. l

To accomplish this result, I provide an aluminum or aluminum type matrixcoated with a non-metallic coating or what is generally termed as anoxide coating.- 1 have discovered that these coatings, when-properlyapplied, increase the life of an aluminum type matrix to a veryappreciable extent and that the application of these coatings to thealuminum matrices insures that each matrix will have a long useful lifeand will produce during that time a type of uniform character.

Application filed September 9,, 1939. serial No. 391,1512.

summon-mu m'rmx In order to provide type molds according to myinvention, I may use anyaluminum alloy which has a sufiicie'nt hardnessand such other well known metallurgical characteris-' tics as arenecessary for this purpose, but

since the material from which type matrices v are made should be of someconsiderable metallurgical hardness, I prefer to use those 1 aluminumalloys which are susceptible to heat treatment and in which, by means ofsuch heat treatment, a high metallurgical hardness is produced. The termalumi num, as used herein and in. the appended claim, refers to aluminumbase allo s containing more than about 80 per cent 0 aluminum and one ormore of those various alloying constituents such as cop er, manganese,magnesium, zinc, silicon, nic el, iron, chromium, etc. which are addedto aluminum, as is well known to the art, for the purpose of producingalloys of ahardness greater than that of aluminum.

In providing such aluminum type matrices as above mentioned with anon-metallic coating, I have used several of the processes by whichnon-metallic or oxide coatings have heretofore been formed on aluminum.These processes which, for the most part, depend upon the action ofchemical solution on the aluminum surface with or without thefurappearsto best produce the coating desired. Into such a solution, which hasbeen broughtto a temperature of about Centigrade, the aluminum typematrix. is dipped for ,a

period of about 1 to 5 minutes, at theend of which time the-coatingdesired is produced.-

The term oxide coating designation of the art which describes a layer ofoxide produced on i 0.2% of potassium dichromate since I have found thatof'the known-solutionsthis one g y as used-herein" and 1n the appendedclaim, is a well known aluminum or aluminum alloy surfaces by treatmentof the metal surfaces with acids, such assulfuric, chromic, etc., oralkalies, suchas sodium carbonate or the alkali sul- 6 fates and acidsulfates such as'sodium sulfate or sodium acid sulfate, etc, all with orwithout the addition of other substances and with or without the use ofexternally-applied electrical energy; The term oxide coating does 10 notinclude the very thin film of aluminum oxide which is naturally formedupon that metal or its alloys by reason of contact with the air.

Aluminumtype matrices which have been 15 .coated according to the aboveprocedure have been found to be very satisfactory.' For instance, a.number of matrices which were so treated withstood the. action ofthe hottype )netal for a total of 5,000 casting operations .20 without showingsigns of failure. The significance of this remarkable erformance w1ll bereadily understood when 1t is realized that matrices made from aluminumalloys and uncoated rarely produced over about 100 to 5 150 castswithout failure and many of them failed after only a few casts.

Having thus described the nature and benefits of my invention and themethods by which it may be performed, I claim: A type matrix made ofaluminum and provided with a hard adherent oxide coatir ia WELKERWALLACE WEN

